Transmission for a Motor Vehicle, Motor Vehicle Powertrain, and Method for Operating a Transmission

ABSTRACT

A transmission (G) for a motor vehicle includes an electric machine (EM1), a first input shaft (GW1), a second input shaft (GW2), an output shaft (GWA), two planetary gear sets (P1, P2, P3), and at least six shift elements (A, B, C, D, E, F). Different gears are implementable by selectively actuating the at least six shift elements (A, B, C, D, E, F) and, in addition, in interaction with the electric machine (EM1), different operating modes are implementable. A drive train for a motor vehicle with such transmission (G) and a method for operating such transmission (G) are also provided.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is related and has right of priority to GermanPatent Application No. 102018215226.8 filed in the German Patent Officeon Sep. 7, 2018 and is a nationalization of PCT/EP2019/071039 filed inthe European Patent Office on Aug. 5, 2019, both of which areincorporated by reference in their entirety for all purposes.

FIELD OF THE INVENTION

The invention relates generally to a transmission for a motor vehicle,including an electric machine, a first input shaft, a second inputshaft, an output shaft, and a first planetary gear set, a secondplanetary gear set, and a third planetary gear set. The planetary gearsets each include multiple elements, wherein a first shift element, asecond shift element, a third shift element, a fourth shift element, afifth shift element, and a sixth shift element are provided. A rotor ofthe electric machine is connected to the second input shaft. Moreover,the invention relates generally to a motor vehicle drive train, in whichthe transmission is utilized, and to a method for operating thetransmission.

BACKGROUND

In hybrid vehicles, transmissions are known which also include, inaddition to a gear set, one or multiple electric machine(s). In thiscase, the transmission is usually configured to be multi-stage, i.e.,multiple different transmission ratios are selectable, as gears, betweenan input shaft and an output shaft by actuating appropriate shiftelements, wherein this is preferably automatically carried out.Depending on the arrangement of the shift elements, the shift elementsare clutches or brakes. The transmission is utilized in this case forsuitably implementing an available tractive force of a prime mover ofthe motor vehicle with respect to various criteria. In this case, thegears of the transmission are mostly also utilized in interaction withthe at least one electric machine for implementing purely electricdriving. Frequently, the at least one electric machine can also beintegrated in the transmission in order to implement various operatingmodes in different ways.

DE 10 2014 218 610 A1 describes a transmission fora hybrid vehicle,which includes, in addition to a first input shaft and an output shaft,three planetary gear sets and an electric machine. Moreover, in onevariant, six shift elements are provided, via which different powerpaths are achieved from the first input shaft to the output shaft whileimplementing different gears and, in addition, different integrations ofthe electric machine can be configured. Here, purely electric drivingcan also be implemented simply by transmitting power via the electricmachine.

SUMMARY OF THE INVENTION

Example aspects of the present invention provide a transmission for amotor vehicle, with which, with a compact design, different operatingmodes can be implemented in a suitable way.

According to example aspects of the invention, a transmission includesan electric machine, a first input shaft, a second input shaft, anoutput shaft, as well as a first planetary gear set and a secondplanetary gear set. The planetary gear sets include multiple elements,wherein, preferably, a first element, a second element, and a thirdelement are associated with each of the planetary gear sets. Inaddition, a first shift element, a second shift element, a third shiftelement, a fourth shift element, and a fifth shift element are provided,via the selective actuation of which different power paths can beimplemented while shifting different gears. It is particularly preferredwhen, from the ratio, at least three different gears can be formedbetween the first input shaft and the output shaft that differ in termsof ratio, wherein a rotor of the electric machine is connected to thesecond input shaft.

Within the meaning of the invention, a “shaft” is understood to be arotatable component of the transmission, via which associated componentsof the transmission are rotationally fixed to each other or via which aconnection of this type is established upon actuation of an appropriateshift element. The particular shaft can connect the components to eachother axially or radially or also both axially and radially. Theparticular shaft can also be present as an intermediate piece, via whicha particular component is connected, for example, radially.

Within the meaning of the invention, “axially” means an orientation inthe direction of a longitudinal central axis, along which the planetarygear sets are arranged coaxially to one another. “Radially” is thenunderstood to mean an orientation in the direction of the diameter of ashaft that lies on this longitudinal central axis.

Preferably, the output shaft of the transmission includes a toothsystem, via which the output shaft is then operatively connected, in themotor vehicle drive train, to a differential gear arranged axiallyparallel to the output shaft. In this case, the tooth system ispreferably provided at a mounting interface of the output shaft, whereinthis mounting interface of the output shaft is preferably situatedaxially in the area of an end of the transmission, at which a mountinginterface of the first input shaft is also provided, the mountinginterface establishing the connection to the upstream prime mover. Thistype of arrangement is particularly suitable for the application in amotor vehicle with a drive train aligned transversely to the directionof travel of the motor vehicle.

Alternatively, an output of the transmission can also be provided, inprinciple, at an axial end of the transmission situated opposite to amounting interface of the first input shaft. In this case, a mountinginterface of the output shaft is then designed at an axial end of theoutput shaft coaxially to a mounting interface of the first input shaft,so that the input and the output of the transmission are located atopposite axial ends of the transmission. A transmission configured inthis way is suitable for the application in a motor vehicle with a drivetrain aligned in the direction of travel of the motor vehicle.

The planetary gear sets are preferably arranged in the sequence firstplanetary gear set, second planetary gear set, and, finally, thirdplanetary gear set axially following the mounting interface of the firstinput shaft. In example aspects, an alternative arrangement of theplanetary gear sets can also be implemented in the axial direction,provided the connection of the elements of the planetary gear setsallows this.

Advantageously, the output shaft is rotationally fixed to the secondelement of the second planetary gear set and rotationally fixed to thethird element of the first planetary gear set and is rotationallyfixable to the first input shaft by the first shift element.

In addition, a second element of the first planetary gear set isrotationally fixed to a third element of the second planetary gear set.In addition, the first input shaft is rotationally fixable by the secondshift element to the second element of the first planetary gear set andto the third element of the second planetary gear set. In addition, thefirst element of the second planetary gear set is fixable at arotationally fixed component by the third shift element.

The first element of the first planetary gear set is fixable at therotationally fixed component by the fourth shift element. The secondinput shaft can be rotationally fixed to the second element of the firstplanetary gear set by the fifth shift element and rotationally fixed tothe first element of the first planetary gear set by the sixth shiftelement.

The first, second, fifth, and sixth shift elements are preferablyclutches, which, upon actuation, each synchronize, if necessary, theparticular components of the transmission joined directly to theclutches, with respect to turning motions of the particular componentsand, thereafter, connect the components to each other in a rotationallyfixed manner.

The third shift element and the fourth shift element can be, inparticular, brakes, which, upon actuation, fix the first element of thefirst planetary gear set or of the second planetary gear set,respectively, and, consequently, prevents a turning motion thereof.

A particular rotationally fixed connection of the rotatable componentsof the transmission is preferably implemented, according to exampleaspects of the invention, via one or also multiple intermediateshaft(s), which can also be present, in this case, as short intermediatepieces when the components are positioned in a spatially dense manner.Specifically, the components that are permanently rotationally fixed toeach other can each be present either as individual components that arerotationally fixed to each other, or also as single pieces. In thesecond case mentioned above, the particular components and theoptionally present shaft are then formed by one common component,wherein this is implemented, in particular, for the case in which theparticular components are situated spatially close to one another in thetransmission.

In the case of components of the transmission that are rotationallyfixed to each other only upon actuation of a particular shift element, aconnection is also preferably implemented via one or also multipleintermediate shaft(s).

A fixation takes place, in particular, by way of a rotationally fixedconnection to a rotationally fixed component of the transmission, whichis preferably a permanently non-rotating component, preferably a housingof the transmission, a part of such a housing, or a componentrotationally fixed thereto.

Within the meaning of the invention, the “connection” of the rotor ofthe electric machine to the second input shaft of the transmission is tobe understood as a connection of such a type that a constantrotational-speed dependence prevails between the rotor of the electricmachine and the second input shaft.

Overall, a transmission according to example aspects of the invention isdistinguished by a compact design, low component loads, good gearingefficiency, and low losses.

According to one example embodiment of the invention, selectiveengagement of the six shift elements results in three gears between thefirst input shaft and the output shaft that differ in terms of ratio. Afirst gear can be implemented between the first input shaft and theoutput shaft by actuating the second shift element and the third shiftelement, in which travel takes place with the simultaneous integrationof a prime mover joined at the first input shaft, as well as theelectric machine. Moreover, a first variant of a second gear that iseffective between the first input shaft and the output shaft results byengaging the first shift element and the third shift element. In theprocess, travel is also implemented in each case with the simultaneousintegration of the upstream prime mover as well as the electric machine.In addition, the second gear in a second variant can be implemented byactuating the first and fourth shift elements and in a third variant byactuating the first and second shift elements.

In addition, a third gear can be engaged between the first input shaftand the output shaft by engaging the second shift element and the fourthshift element. Additionally, the fifth or the sixth shift element isactuated in all gears.

If neither the fifth shift element nor the sixth shift element isactuated in the aforementioned shift conditions, travel can take placevia the upstream prime mover. The electric machine can also be decoupledin this case. As a result, zero-load losses of the electric machine canbe avoided. However, a shift into the first three variants of the secondgear has the advantage that the electric machine is also integrated and,as a result, hybrid driving can take place.

Given a suitable selection of stationary transmission ratios of theplanetary gear sets, a transmission ratio range which is suitable forthe application in a motor vehicle is implemented as a result. In thiscase, gear shifts between the gears are implementable, in which only thecondition of two shift elements (since the fifth or the sixth shiftelement always remains engaged in the hybrid mode), in each case, isalways to be varied, in that one of the shift elements contributing tothe preceding gear is to be disengaged and another shift element is tobe engaged in order to implement the subsequent gear. As a furtherconsequence thereof, a shift between the gears can take place veryrapidly.

Due to the connection of the electric machine to the second input shaftof the transmission, different operating modes can also be achieved in asimple way:

A first gear between the second input shaft and the output shaft can beutilized for purely electric driving, wherein this first gear results byengaging the third shift element and the sixth shift element. The ratioof the first gear is shorter or less than the firstinternal-combustion-engine gear.

In addition, a second gear can be implemented between the second inputshaft and the output shaft for purely electric driving. The third shiftelement and the fifth shift element are to be actuated in order toengage this second gear. A ratio of this second gear, which is effectivebetween the second input shaft and the output shaft, corresponds to aratio of the first gear between the first input shaft and the outputshaft.

In addition, a third gear can be implemented between the second inputshaft and the output shaft for purely electric driving. The fourth shiftelement and the fifth shift element are to be actuated in order toengage this second gear. A ratio of this third gear, which is effectivebetween the second input shaft and the output shaft, corresponds to aratio of the second gear between the first input shaft and the outputshaft.

Starting from purely electric driving in the first gear, which iseffective between the second input shaft and the output shaft, theupstream prime mover can then be started into the first gear, which iseffective between the first input shaft and the output shaft. Inaddition, starting from the first electric gear or e-gear, a start cantake place into the first variant of the second gear. The third shiftelement and the sixth shift element are engaged in each of the twogears.

Likewise, a start of the upstream prime mover into the first gear andinto the second variant of the second gear, which is effective betweenthe first input shaft and the output shaft, can also take place from thesecond gear, which is effective between the second input shaft and theoutput shaft, since the third shift element and the fifth shift elementare engaged.

Likewise, a start of the upstream prime mover into the second variantand into the third gear, which is effective between the first inputshaft and the output shaft, can also take place from the third gear,which is effective between the second input shaft and the output shaft,since the fourth shift element and the fifth shift element are engaged.

As a further operating mode, a charging operation of an electricaccumulator can also be implemented, in that the second shift elementand the fifth shift element are engaged and, therefore, a rotationallyfixed connection between the first input shaft and the second inputshaft and, therefore, also a coupling with the electric machine areestablished. At the same time, a force-fit connection to the outputshaft is not established, and therefore the transmission is in a neutralposition. Apart from a charging operation, a start of the upstream primemover via the electric machine can also be implemented as a result.

Moreover, powershifts with tractive force support can be implemented:during the gearchange between the first gear, which is effective betweenthe first input shaft and the output shaft, and the first variant of thesecond gear, which is effective between the first input shaft and theoutput shaft, the tractive force with the third shift element engagedand with the fifth or sixth shift element engaged can be supported viathe electric machine, wherein the synchronization of the shift elementto be engaged takes place via a closed-loop control of the rotationalspeed of the upstream prime mover. Alternatively, however, this can alsotake place by using synchronized shift elements or also by usinganother, separate synchronizing mechanism, such as a transmission brakeor also one further electric machine, which can be operatively connecteddirectly or indirectly to the first input shaft. If one further shiftelement, as a separating clutch, is also provided on the input side ofthe input shaft, the inertial mass of the upstream drive machine can bedecoupled during the synchronization.

Likewise, a gearchange under load can also take place between the secondvariant of the second gear, which is effective between the first inputshaft and the output shaft, and the third gear, which is effectivebetween the first input shaft and the output shaft, with the fourthshift element and the fifth shift element engaged.

The transmission according to example aspects of the invention can alsobe operated in such a way that a rotational-speed reduction of theelectric machine is achieved during driving. It is therefore possible toinitially drive in a hybrid manner in the first variant of the secondgear, in that the third shift element initially remains engaged eitherafter a gear shift from the first gear into the second gear with torquesupport via the electric machine or after a start of the prime moverinto the second gear. In order to now reduce a rotational speed of theelectric machine in the first variant of the second gear at higherground speeds, however, a change-over can be implemented from the firstvariant of the second gear into the second variant of the second gear,since the rotor of the electric machine has a lower rotational speedhere than in the first variant of the second gear. This change-overtakes place while preserving the tractive force via the upstream primemover with the first shift element and the fifth shift element engaged.Initially, the load-free, third shift element is disengaged and,subsequent thereto, the load-free, fourth shift element is engaged,wherein the rotational-speed adaptation takes place via closed-loopcontrol of the rotational speed of the electric machine.

A separate shift element is not necessary for decoupling the upstreamprime mover, since, in the second variant of the second gear, which iseffective between the first input shaft and the output shaft, theupstream prime mover can be decoupled by disengaging the first shiftelement. As a result, the second gear is then implemented, which iseffective between the second input shaft and the output shaft.

In addition, in the case of a vehicle that is slowing down, a downshiftfrom the second gear, which is effective between the first input shaftand the output shaft, into the first gear, which is effective betweenthe first input shaft and the output shaft, can be prepared, in that,initially, a change-over takes place from the second variant into thefirst variant of the second gear and, in the process, the tractive forceis preserved via the upstream prime mover with the first shift elementengaged. In the first variant of the second gear, the third shiftelement is then engaged, which becomes necessary in order to support thetractive force via the electric machine as part of the downshift fromthe second gear into the first gear.

One further example embodiment of the invention is to provide atransmission, wherein a seventh shift element is provided, which isarranged and designed for connecting two elements of the first planetarygear set P1 or two elements of the second planetary gear set P2 to eachother. In other words, one of the two planetary gear sets is interlockedby the seventh shift element in the actuated condition. Due to theconnection of the two planetary gear sets, as a result of the interlockof the one planetary gear set, the other planetary gear set is alsosimultaneously interlocked.

The interlock preferably takes place via a rotationally fixed connectionof

-   -   the first element with the second element of the second        planetary gear set,    -   the second element with the third element of the first planetary        gear set,    -   the first element with the second element of the first planetary        gear set, or    -   the second element with the third element of the second        planetary gear set.

It is particularly preferred when an additional electric gear isimplementable between the second input shaft and the output shaft byengaging the fifth shift element and the seventh shift element.

By the seventh shift element, a fourth electric gear is thereforeimplementable, which corresponds to the second hybrid gear (directdrive). The ratio of the fourth gear is situated between the ratio ofthe second electric gear and the ratio of the third electric gear. Thefourth electric gear is then also engageable when the fifth and seventhshift elements are engaged.

With this preferred example embodiment, a hybrid transmission isprovided, which has precisely three internal-combustion-engine gears andprecisely four purely electric gears. Finely stepped electric gears havethe advantage that the electric machine can be operated with highefficiency during purely electric driving at a favorable operatingpoint.

As one further example design option of the invention, a furtherelectric machine is provided, the rotor of which is connected at thefirst input shaft. Such an example embodiment has the advantage thatfurther driving modes can be achieved as a result. In addition, as aresult, a start of the upstream prime mover can be implementedimmediately, if necessary, if the prime mover is designed as an internalcombustion engine. In addition, the additional electric machine cansupport the upstream prime mover in the synchronization of shiftelements.

According to one further example embodiment of the invention, the firstinput shaft can be connected in a rotationally fixed manner, via aneighth shift element, to a connection shaft, which, in turn, is thenpreferably coupled within a motor vehicle drive train to the prime moverconnected upstream from the transmission. The eighth shift element canbe designed, in principle, as a force-locking or also as a form-lockingshift element in this case, although it is particularly preferred whenthe eighth shift element is a dog clutch. Via the eighth shift element,the upstream prime mover can therefore also be completely decoupled fromthe transmission, so that a purely electric operation is implementablein a problem-free manner.

In one example refinement of the invention, one or multiple shiftelement(s) is/are each implemented as a form-locking shift element. Inthis case, the particular shift element is preferably designed either asa constant-mesh shift element or as a lock-synchronizer mechanism.Form-locking shift elements have the advantage over friction-lockingshift elements that lower drag losses occur in the disengaged condition,and therefore a better efficiency of the transmission can be achieved.In particular, in the transmission according to example aspects of theinvention, all shift elements are implemented as form-locking shiftelements, and therefore the lowest possible drag losses can be achieved.In principle, however, one shift element or multiple shift elementscould also be configured as force-locking shift elements, for example,as lamellar shift elements.

Within the scope of example aspects of the invention, the planetary gearsets can each be a minus planetary gear set, provided it allows for aconnection of the elements, wherein the first element of the particularplanetary gear set is a sun gear, the second element of the particularplanetary gear set is a planet carrier, and the third element of theparticular planetary gear set is a ring gear. A minus planetary gear setis composed, in a way known, in principle, to a person skilled in theart, of the elements sun gear, planet carrier, and ring gear, whereinthe planet carrier, rotatably mounted, guides at least one planet gear,although preferably multiple planet gears, which each individuallyintermesh with the sun gear as well as with the surrounding ring gear.

Alternatively thereto, one planetary gear set or also multiple planetarygear sets can also be a plus planetary gear set, however, provided itallows for the connection of the particular elements, wherein the firstelement of the particular planetary gear set is then a sun gear, thesecond element of the particular planetary gear set is a ring gear, andthe third element of the particular planetary gear set is a planetcarrier. In a plus planetary gear set as well, the elements sun gear,ring gear, and planet carrier are present, wherein the planet carrierguides at least one planet gear pair, in which one planet gear is meshedwith the internal sun gear and the other planet gear is meshed with thesurrounding ring gear, and the planet gears are intermeshed with eachother.

Where permitted by a connection of the individual elements, a minusplanetary gear set can be converted into a plus planetary gear set,wherein, as compared to the design as a minus planetary gear set, thering gear connection and the planet carrier connection are to beinterchanged, and a stationary transmission ratio is to be increased byone. Conversely, a plus planetary gear set could also be replaced by aminus planetary gear set, provided the connection of the elements of thetransmission enables this. In this case, as compared to the plusplanetary gear set, the ring gear connection and the planet carrierconnection would also need to be interchanged, and a stationarytransmission ratio would need to be reduced by one. Within the scope ofexample aspects of the invention, the three planetary gear sets are eachpreferably designed as a minus planetary gear set, however.

According to one further example embodiment of the invention, the firstshift element and the second shift element are combined to form oneshift element pair, with which one actuating element is associated. Thefirst shift element, on the one hand, and the second shift element, onthe other hand, can be actuated via the actuating element starting froma neutral position. This has the advantage that, due to thiscombination, the number of actuating elements can be reduced and,therefore, the manufacturing complexity can also be reduced.

Alternatively or also in addition to the aforementioned examplevariants, the third shift element and the fourth shift element arecombined to form one shift element pair, with which one actuatingelement is associated. The third shift element, on the one hand, and thefourth shift element, on the other hand, can be actuated via thisactuating element starting from a neutral position. As a result, themanufacturing complexity can be reduced, in that, due to the combinationof the two shift elements to form one shift element pair, one actuatingunit can be utilized for both shift elements.

Alternatively to the aforementioned example variant, the fifth shiftelement and the sixth shift element are combined to form one shiftelement pair, with which one actuating element is associated. The fifthshift element, on the one hand, and the sixth shift element, on theother hand, can be actuated via this actuating element starting from aneutral position. As a result, the manufacturing complexity can bereduced, in that, due to the combination of the two shift elements toform one shift element pair, one actuating unit can be utilized for bothshift elements.

It is particularly preferred when all six shift elements are combined toform particular shift element pairs. In this way, advantageously, sixshift elements can be actuated with only three actuators.

In one example variant with seven shift elements, it is preferred, inparticular, when the third shift element and the seventh shift elementare combined to form one shift element pair, with which one actuatingelement is associated, wherein, via the actuating element, the thirdshift element, on the one hand, and the seventh shift element, on theother hand, are actuatable from a neutral position.

According to one example embodiment of the invention, the rotor of theelectric machine is rotationally fixed to the second input shaft.Alternatively, according to one example design option of the invention,the rotor is connected to the second input shaft via at least one gearstage. The electric machine can be arranged either coaxially to theplanetary gear sets or so as to lie axially offset with respect thereto.In the former case, the rotor of the electric machine can either berotationally fixed directly to the second input shaft or can be coupledthereto via one or also multiple intermediate gear stage(s), wherein thelatter allows for a more favorable configuration of the electric machinewith higher rotational speeds and lower torques. The at least one gearstage can be designed as a spur gear stage and/or as a planetary gearstage in this case. In the case of a coaxial arrangement of the electricmachine, the two planetary gear sets can then also, more preferably, bearranged axially in the area of the electric machine as well as radiallyinternally with respect thereto, so that the axial installation lengthof the transmission can be shortened.

If the electric machine is provided axially offset with respect to theplanetary gear sets, however, a coupling takes place via one or multipleintermediate gear stage(s) and/or a flexible traction drive mechanism.The one or the multiple gear stage(s) can also be implementedindividually, in this case, either as a spur gear stage or as aplanetary gear stage. A flexible traction drive mechanism can be eithera belt drive or a chain drive.

If a further electric machine is also provided, a rotor of this furtherelectric machine can also be either rotationally fixed to the firstinput shaft directly or can be coupled to the first input shaft via atleast one gear stage. The at least one gear stage can be a spur gearstage or a planetary gear stage or also a flexible traction drivemechanism. In addition, the further electric machine can be providedcoaxially or also axially offset with respect to the first input shaftand, therefore, also to the planetary gear sets.

Within the scope of example aspects of the invention, a startingcomponent can be installed upstream from the transmission, for example ahydrodynamic torque converter or a friction clutch. This startingcomponent can then also be an integral part of the transmission and actsto configure a starting process, in that the starting component enablesa slip speed between the prime mover, which is designed, in particular,as an internal combustion engine, and the first input shaft of thetransmission. In this case, one of the shift elements of thetransmission or the separating clutch, which may be present, can also bedesigned as such a starting component, in that the starting component ispresent as a frictional shift element. In addition, a one-way clutchwith respect to the transmission housing or to another shaft can bearranged on each shaft of the transmission, in principle.

The transmission according to example aspects of the invention is, inparticular, part of a motor vehicle drive train for a hybrid or electricvehicle and is then arranged between a prime mover of the motor vehicle,which is configured as an internal combustion engine or as an electricmachine, and further components of the drive train, which are arrangeddownstream in the direction of power flow to driving wheels of the motorvehicle. In this case, the first input shaft of the transmission iseither permanently coupled to a crankshaft of the internal combustionengine or to the rotor shaft of the electric machine in a rotationallyfixed manner or can be connected thereto via an intermediate separatingclutch or a starting component, wherein a torsional vibration damper canalso be provided between an internal combustion engine and thetransmission. On the output end, the transmission is then preferablycoupled, within the motor vehicle drive train, to a differential gear ofa drive axle of the motor vehicle, wherein a connection to an interaxledifferential can also be present in this case, however, via which adistribution to multiple driven axles of the motor vehicle takes place.The differential gear or the interaxle differential can be arranged withthe transmission in one common housing in this case. A torsionalvibration damper, which is optionally present, can also be integratedinto this housing.

Within the meaning of the invention, the expressions that two componentsof the transmission are “connected” or “coupled” or “are connected toeach other” mean a permanent coupling of these components, and thereforesaid components cannot rotate independently of each other. In thatrespect, no shift element is provided between these components, whichcan be elements of the planetary gear sets and/or also shafts and/or arotationally fixed component of the transmission. Instead, theappropriate components are coupled to each other with a constantrotational speed dependence.

However, if a shift element is provided between two components, thesecomponents are not permanently coupled to each other. Instead, acoupling is carried out only by actuating the intermediate shiftelement. In this case, an actuation of the shift element means, withinthe meaning of the invention, that the particular shift element istransferred into an engaged condition and, consequently, synchronizesthe turning motions, if necessary, of the components connected directlythereto. In the case of an example embodiment of the particular shiftelement as a form-locking shift element, the components directlyconnected to each other in a rotationally fixed manner via the shiftelement rotate at the same rotational speed, while, in the case of aforce-locking shift element, speed differences can exist between thecomponents also after an actuation of the same shift element. Thisintentional or also unintentional condition is nevertheless referred to,within the scope of the invention, as a rotationally fixed connection ofthe particular components via the shift element.

The invention is not limited to the specified combination of features ofthe main claim or the claims dependent thereon. In addition, individualfeatures can be combined with one another, provided they arise from theclaims, the description of preferred embodiments of the invention whichfollows, or directly from the drawings. References in the claims to thedrawings via the use of reference signs is not intended to limit thescope of protection of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantageous example embodiments of the invention, which are explainedin the following, are represented in the drawings. Wherein:

FIG. 1 shows a diagrammatic view of a motor vehicle drive train;

FIGS. 2 and 3 each show a diagrammatic view of a transmission of thetype that can be utilized in the motor vehicle drive train from FIG. 1;

FIG. 4 shows an exemplary shift pattern for a transmission from FIGS. 2and 3;

FIG. 5 shows a diagrammatic view of a transmission of the type that canalso be utilized in the motor vehicle drive train from FIG. 1;

FIG. 6 shows a diagrammatic view of a transmission of the type that canalso be utilized in the motor vehicle drive train from FIG. 1;

FIGS. 7 and 8 shows an exemplary shift pattern for a transmissionaccording to FIG. 5; and

FIGS. 9 through 14 each show a schematic of a modification of thetransmissions from FIGS. 2 through 5 as well as FIG. 7.

DETAILED DESCRIPTION

Reference will now be made to embodiments of the invention, one or moreexamples of which are shown in the drawings. Each embodiment is providedby way of explanation of the invention, and not as a limitation of theinvention. For example, features illustrated or described as part of oneembodiment can be combined with another embodiment to yield stillanother embodiment. It is intended that the present invention includethese and other modifications and variations to the embodimentsdescribed herein.

FIG. 1 shows a diagrammatic view of a motor vehicle drive train of ahybrid vehicle, wherein, in the motor vehicle drive train, an internalcombustion engine VKM is connected to a transmission G via anintermediate torsional vibration damper TS. Connected downstream fromthe transmission G, on the output end thereof, is a differential gearAG, via which drive power is distributed to driving wheels DW of a driveaxle of the motor vehicle. The transmission G and the torsionalvibration damper TS are arranged in a common housing of the transmissionG in this case, into which the differential gear AG can then also beintegrated. As is also apparent in FIG. 1, the internal combustionengine VKM, the torsional vibration damper TS, the transmission G, andalso the differential gear AG are aligned transversely to a direction oftravel of the motor vehicle.

FIG. 2 shows a schematic of the transmission G according to a firstexample embodiment of the invention. As is apparent, the transmission Gincludes of a gear set RS and an electric machine EM1, which are botharranged in the housing of the transmission G. The gear set RS includestwo planetary gear sets P1 and P2, wherein each of the planetary gearsets P1 and P2 includes a first element E11 and E12, respectively, asecond element E21 and E22, respectively, and a third element E31 andE32, respectively. The first element E11 and E12 is formed by a sun gearof the planetary gear set P1 and P2, respectively, while the secondelement E21 and E22 of the planetary gear set P1 and P2, respectively,is present as a planet carrier, and the third element E31 and E32 of theplanetary gear set P1 and P2, respectively, is present as a ring gear.

In the present case, the first planetary gear set P1 and the secondplanetary gear set P2 are each therefore present as a minus planetarygear set. The particular planet carrier thereof guides at least oneplanet gear in a rotatably mounted manner; the planet gear is meshedwith the particular radially internal sun gear as well as with theparticular radially surrounding ring gear. It is particularly preferred,however, when multiple planet gears are provided in the case of thefirst planetary gear set P1 and in the case of the second planetary gearset P2.

As is apparent in FIG. 2, the transmission G includes a total of sixshift elements in the form of a first shift element A, a second shiftelement B, a third shift element C, a fourth shift element D, a fifthshift element E, and a sixth shift element F. The shift elements A, B,C, D, E, and F are each designed as form-locking shift elements and arepreferably present as constant-mesh shift elements. While the thirdshift element C and the fourth shift element D are each a brake, theremaining shift elements A, B, E, and F are clutches.

The first element E11 of the first planetary gear set P1 is fixable bythe fourth shift element D at a rotationally fixed component GG, whichis the transmission housing of the transmission G or a portion of thistransmission housing. The first element E12 of the second planetary gearset P2 is fixable at the rotationally fixed component GG by the thirdshift element C.

The third element E31 of the first planetary gear set P1 and the secondelement E22 of the second planetary gear set P2 are connected in arotationally fixed manner to an output shaft GWA of the transmission G.The second element E22 of the second planetary gear set P2 and the thirdelement E31 of the first planetary gear set P1 and, therefore, also theoutput shaft GWA are jointly rotationally fixable to a first input shaftGW1 of the transmission G by engaging the first shift element A.

A second input shaft GW2 is rotationally fixable to the second elementE21 of the first planetary gear set P1 by the fifth shift element E androtationally fixable to the first element E11 of the first planetarygear set P1 by the sixth shift element F.

The second input shaft GW2 of the transmission G is also permanentlyrotationally fixed to a rotor R1 of an electric machine EM1, the statorS1 of which is continuously fixed at the rotationally fixed componentGG.

The first input shaft GW1 as well as the output shaft GWA form amounting interface GW1-A and GWA-A, respectively, wherein the mountinginterface GW1-A in the motor vehicle drive train from FIG. 1 is utilizedfor a connection at the internal combustion engine VKM, while thetransmission G is connected at the mounting interface GWA-A to thedownstream differential gear AG. The mounting interface GW1-A of thefirst input shaft GW1 is formed at an axial end of the transmission G,while the mounting interface GWA-A of the output shaft GWA is situatedin the area of the same axial end and, here, is aligned transversely tothe mounting interface GW1-A of the first input shaft GW1. In addition,the first input shaft GW1, the second input shaft GW2, and the outputshaft GWA are arranged coaxially to one another.

The planetary gear sets P1 and P2 are also situated coaxially to theinput shafts GW1 and GW2 and the output shaft GWA, wherein the planetarygear sets P1 and P2 are arranged in the sequence first planetary gearset P1 and second planetary gear set P2 axially subsequent to themounting interface GW1-A of the first input shaft GW1. Likewise, theelectric machine EM1 is also located coaxially to the planetary gearsets P1 and P2 and, therefore, also to the input shafts GW1 and GW2 andto the output shaft GWA, wherein the electric machine EM1 is arrangedaxially spaced apart from the first planetary gear set P1 and the secondplanetary gear set P2.

As is also apparent from FIG. 2, the first shift element A and thesecond shift element B are arranged axially between the first planetarygear set P1 and the second planetary gear set P2, wherein, here, thesecond shift element B is situated axially adjacent to the firstplanetary gear set P1, followed axially by the first shift element A.

The third shift element C is situated axially on a side of the secondplanetary gear set P2 facing away from the first planetary gear set P1.The fourth shift element D, the fifth shift element E, and the sixthshift element F are situated axially on a side of the first planetarygear set P1 facing away from the second planetary gear set P2.

The first shift element A and the second shift element B are situatedaxially directly next to each other and radially at the same level andare combined to form one shift element pair SP1, in that a commonactuating element is associated with the first shift element A and thesecond shift element B, via which the first shift element A, on the onehand, and the second shift element B, on the other hand, can be actuatedfrom a neutral position.

The third shift element C and the fourth shift element D are spatiallyseparated from each other by the shift elements A, B and are combined toform one shift element pair SP2, in that a common actuating element isassociated with the third shift element C and the fourth shift elementD, via which the third shift element C, on the one hand, and the fourthshift element D, on the other hand, can be actuated from a neutralposition.

Likewise, the fifth shift element E and the sixth shift element F arecombined to form one shift element pair SP3, in that a common actuatingelement is associated with the fifth shift element E and the sixth shiftelement F, via which the fifth shift element E, on the one hand, and thesixth shift element F, on the other hand, can be actuated from a neutralposition.

FIG. 3 shows a diagrammatic view of a transmission G according to asecond example design option of the invention, which can also beutilized in the motor vehicle drive train in FIG. 1. This design optionlargely corresponds to the preceding example variant according to FIG.2, with the difference that the sequence of the planetary gear sets P1,P2 is interchanged. As a result, the first electric machine EM1 is nowno longer located axially next to the planetary gear sets P1 and P2, butrather essentially axially at the level thereof and radially surroundsthe planetary gear sets P1 and P2. As a result, the transmission can bedesigned to be axially even more compact. Otherwise, the example designoption according to FIG. 3 corresponds to the example variant accordingto FIG. 2, and therefore reference is made to the description thereof.

FIG. 4 shows an exemplary shift pattern for the transmission G fromFIGS. 2 and 3 in table form. As is apparent, a total of three gears 1through 3, which differ in terms of the ratio, are implementable betweenthe first input shaft GW1 and the output shaft GWA, wherein, in thecolumns of the shift pattern, an X indicates which of the shift elementsA through F is engaged in which of the gears 1 through 3.

As is apparent in FIG. 4, a first gear 1 is implemented between thefirst input shaft GW1 and the output shaft GWA by actuating the secondshift element B and the third shift element C.

In addition, a second gear 2 can be implemented between the first inputshaft GW1 and the output shaft GWA in a first variant 2.1 by actuatingthe first shift element A and the third shift element C, wherein thesecond gear can also be formed in a second variant 2.2 by engaging thefirst shift element A and the fourth shift element D, and in a thirdvariant 2.3 by actuating the first shift element A and the second shiftelement B.

In addition, a third gear 3 also results between the first input shaftGW1 and the output shaft GWA by actuating the second shift element B andthe fourth shift element D.

In all the aforementioned gears, additionally, either the fifth shiftelement E or the sixth shift element F is engaged.

Although the shift elements A through F are each designed as aform-locking shift element, a shift between the first gear 1 and thefirst variant 2.1 of the second gear can be implemented under load,since the third shift element C contributes thereto in each case. Here,the first electric machine EM1 is connected either to the first elementE11 or to the second element E21 of the first planetary gear set P1.

In addition, a shift between the second variant 2.2 of the second gearand the third gear 3 can be implemented under load, since the fourthshift element D contributes thereto. Here, the first electric machineEM1 is connected to the second element E21 of the first planetary gearset P1.

A synchronization during the gear shifts can take place in each case viaan appropriate closed-loop control of the upstream internal combustionengine VKM, and therefore the particular shift element to be disengagedis disengaged without load and the shift element to be subsequentlyengaged can be engaged without load.

The transmissions G from FIGS. 2 and 3 can also be operated inalternative operating modes with the aid of the electric machine EM1.Purely electric driving can take place in a first gear E0, which iseffective between the second input shaft GW2 and the output shaft GWAand, for the implementation of which, the third shift element C and thesixth shift element F are to be transferred into an engaged condition.As a result, with the third shift element C and the sixth shift elementF engaged, the first electric machine EM1 is directly connected to theoutput shaft GWA with a constant ratio. The ratio of the first gear E0is shorter or less than the first internal-combustion-engine gear 1.

In addition, purely electric driving can take place in a second gear E1,which is effective between the second input shaft GW2 and the outputshaft GWA and, for the implementation of which, the third shift elementC and the fifth shift element E are to be transferred into an engagedcondition. With the third shift element C and the fifth shift element Eengaged, the first electric machine EM1 is connected to the output shaftGWA with a constant ratio (with the element E12 fixed, the third elementE 32 is rotatable with the second element E12 of the second planetarygear set).

The ratio of the second gear E1 corresponds here, in each case, to aratio of the first gear 1 between the first input shaft GW1 and theoutput shaft GWA.

In addition, a third gear E3 can also be implemented between the secondinput shaft GW2 and the output shaft GWA, for the implementation ofwhich the fourth shift element D and the fifth shift element E are to beengaged. As a result, the electric machine EM1 is connected to theoutput shaft GWA with a constant ratio (second element E21 is rotatablewith the third element E31 while the first element E11 of the firstplanetary gear set P1 is fixed). A ratio of this third gear E3corresponds, in each case, to a ratio of the third gear, which iseffective between the first input shaft GW1 and the output shaft GWA.

Advantageously, a start of the internal combustion engine VKM into thefirst gear 1 and into the first variant 2.1 of the second gear 2 can becarried out starting from the first gear E0, since the third shiftelement C and the sixth shift element F are engaged in each of thesegears.

Starting from the second gear E1, a start of the internal combustionengine VKM into the first gear 1 and into the first variant 2.1 of thesecond gear 2 can be carried out, because the third shift element C andthe fifth shift element E contribute thereto.

Starting from the third gear E3, a start of the internal combustionengine VKM into the second variant 2.2 of the second gear and into thethird gear 3 can be carried out, because the fourth and fifth shiftelements D and E are engaged here.

Therefore, a transition from purely electric driving into driving viathe internal combustion engine or into hybrid driving can be carried outrapidly.

If the first electric machine is to be decoupled from the first elementE11 and coupled onto the second element E21 of the first planetary gearset P1, the tractive force can be maintained in the meantime with theinternal combustion engine VKM. This is useful mainly in the first gear1 or the first variant 2.1 of the second gear 2, because the shiftelement D is not engaged there. If the shift element D as well as theshift element F would be simultaneously engaged, the first electricmachine EM1 would be braked.

Moreover, a charging or start function can be implemented by engagingthe second shift element B and the fifth shift element E. This is thecase because, in the engaged condition of the second shift element B andthe fifth shift element E, the second input shaft GW2 is directlycoupled, in a rotationally fixed manner, to the first input shaft GW1and, therefore, also to the internal combustion engine VKM, wherein,simultaneously, there is no force-fit connection to the output shaftGWA. When the electric machine EM1 is operated as a generator, anelectric accumulator can be charged via the internal combustion engineVKM, whereas, when the electric machine EM1 is operated as an electricmotor, a start of the internal combustion engine VKM is implementablevia the electric machine EM1.

In addition, a rotational-speed reduction of the electric machine EM1can be configured in the mechanical or hybrid mode: after a gear shiftfrom the first gear into the second gear, with torque support via theelectric machine EM1, or after a start of the internal combustion engineVKM into the second gear, hybrid driving results, wherein a rotationallyfixed connection exists between the second input shaft GW2 and thesecond element E21, i.e., the fifth shift element E is engaged.

In order to reduce the rotational speed of the electric machine EM inthe second gear at higher ground speeds, a change-over can be carriedout from the first variant 2.1 of the second gear into the secondvariant 2.2, in which the rotor R1 has a lower rotational speed. Thischange-over takes place while preserving the tractive force via theinternal combustion engine VKM with the third shift element C engaged.For this purpose, the third shift element C, which is then load-free, isdisengaged and the likewise load-free, fourth shift element D isengaged, wherein the rotational-speed adaptation takes place in eachcase via a closed-loop control of the rotational speed of the electricmachine EM.

The advantage of utilizing the second variant 2.2 is that the internalcombustion engine VKM, on the one hand, can be decoupled at any time bydisengaging the shift element A also without an additional separatingclutch K0, while the electric machine EM1 drives or decelerates(recuperation) the vehicle. On the other hand, in the case of a vehiclethat is slowing down, a downshift from the second gear into the firstgear can be prepared, in that a change-over from the second variant 2.2into the first variant 2.1 takes place while the internal combustionengine maintains the tractive force (the first shift element A remainsengaged). In the first variant 2.1 of the second gear, the third shiftelement C is engaged, which becomes necessary in order to support thetractive force with the electric machine EM1 during the downshift fromthe second gear into the first gear.

FIG. 5 shows a diagrammatic view of a transmission G according to afurther example design option of the invention, which can also beutilized in the motor vehicle drive train in FIG. 1. This design optionlargely corresponds to the preceding example variant according to FIG.2, wherein the transmission G includes an additional seventh shiftelement K.

The seventh shift element K is arranged in such a way that, in theactuated condition, the seventh shift element K interlocks the secondplanetary gear set P2. Due to the permanently fixed carrier-ring gearconnection of the two planetary gear sets P1 and P2, when the secondplanetary gear set P2 is interlocked, the first planetary gear set P1 isalways also interlocked.

By the seventh shift element G, a fourth electric gear is implementable,which corresponds to the second hybrid gear (direct drive). The ratio ofthe fourth gear E2 is situated between the ratio of the second electricgear E1 and the ratio of the third electric gear E3. In the fourthelectric gear E2, the seventh shift element K and the fifth shiftelement E are engaged.

The fourth electric gear is then also engageable when the seventh shiftelement K and the sixth shift element F are engaged.

With this preferred example embodiment, a hybrid transmission isprovided, which has precisely three internal-combustion-engine gears andprecisely four purely electric gears. Finely stepped electric gears havethe advantage that the electric machine can be operated with highefficiency during purely electric driving at a favorable operatingpoint.

Not represented, but possible, is an interlock also via the rotationallyfixed connection of

-   -   the second element E21 with the third element E31 of the first        planetary gear set P1,    -   the first element E11 with the second element E21 of the first        planetary gear set P1, or    -   the second element E22 with the third element E32 of the second        planetary gear set P2.

In the example embodiment according to FIG. 5, the first shift element Aand the second shift element B are combined to form a first shiftelement pair SP1. The third shift element C and the seventh shiftelement G are combined to form a second shift element pair SP2. Thefifth shift element E and the sixth shift element F are combined to forma third shift element pair SP3. For the rest, the example variantaccording to FIG. 5 corresponds to the example design option accordingto FIG. 2, and therefore reference is made to the description thereof.

Moreover, FIG. 6 shows a schematic of a transmission G according to afurther example embodiment of the invention, of the type which can alsobe utilized in the motor vehicle drive train in FIG. 1. This exampleembodiment essentially corresponds to the example variant according toFIG. 2, wherein, in contrast thereto, the first input shaft GW1 can nowbe rotationally fixed, at the mounting interface GW1-A via an eighthshift element K0, to a connection shaft AN, which is then connected tothe upstream internal combustion engine VKM in the motor vehicle drivetrain. The eighth shift element K0 is configured as a form-locking shiftelement and, particularly preferably, is present as a constant-meshshift element. Moreover, a further electric machine EM2 is alsoprovided, the rotor R2 of which is rotationally fixed to the first inputshaft GW1, while a stator S2 of the further electric machine EM2 isfixed at the rotationally fixed component GG. The rotor R2 is connectedat the first input shaft GW1 axially between the eighth shift element K0and the first planetary gear set P1. For the rest, the example variantaccording to FIG. 6 corresponds to the example design option accordingto FIG. 2, and therefore reference is made to the description thereof.

In FIGS. 7 and 8, different conditions of the motor vehicle drive trainfrom FIG. 1, with utilization of the transmission G from FIG. 6, arerepresented in table form, wherein these different conditions areachieved via different integrations of the two electric machines EM1 andEM2 as well as the internal combustion engine VKM.

First, purely electric driving by a single electric machine anddisengaged shift element K0 is described with reference to FIG. 7.

If the shift element E or F is engaged, purely electric driving ispossible with only one electric machine, as follows.

In the first gear E0, purely electric driving takes place via the firstelectric machine EM1, in that the first gear E0 is implemented in thetransmission G in the way described above with respect to FIG. 4.

In the second gear E1, purely electric driving takes place via the firstelectric machine EM1, in that the second gear E1 is implemented in thetransmission G in the way described above with respect to FIG. 4.

In the fourth gear E3, purely electric driving also takes place via thefirst electric machine EM1, in that the fourth gear E3 is implemented inthe way described above with respect to FIG. 4.

The third gear E2 can be driven by the second electric machine, in thatthe first shift element A and the fifth shift element E are engaged inthe transmission G.

Second, alternative purely electric driving with decoupled firstelectric machine EM1 and disengaged shift element K0 is described.

If neither the fifth shift element E nor the sixth shift element F isengaged, purely electric driving is possible with only the secondelectric machine EM2, as follows.

In the second gear E1, purely electric driving is implemented, in thatthe second and third shift elements B and C are engaged in thetransmission G.

In a first variant E2.1 of the second electric gear, purely electricdriving is implemented, in that the first and third shift elements A andC are engaged in the transmission G.

In a second variant E2.2 of the second electric gear, purely electricdriving is implemented, in that the first and fourth shift elements Aand D are engaged in the transmission G.

In a third variant E2.3 of the second electric gear, purely electricdriving is implemented, in that the first and second shift elements Aand B are engaged in the transmission G.

The third gear E3 can be driven, in that the second shift element B andthe fourth shift element D are engaged in the transmission G.

Third, purely electric driving by both electric machines and disengagedshift element K0 is described with reference to FIG. 8.

The same gear steps or variants can be implemented as described in FIG.4, wherein these can now be driven purely electrically. The hybriddriving and the purely internal combustion engine-driving are notrepresented in FIG. 8. For the rest, reference is made to the commentspresented with respect to FIG. 4.

The advantages of two electric machines can be summarized as follows:

-   -   purely electric powershift, since the second electric machine        EM2, with disengaged shift element K0, performs the functions of        the internal combustion engine;    -   the second electric machine EM2, with disengaged shift element        K0, can be utilized for synchronization, while the first        electric machine EM1 supports the tractive force;    -   a greater total electrical power is implementable with        disengaged shift element K0;    -   a greater range is possible with a hybrid operation;    -   the internal combustion engine VKM can be started by the second        electric machine EM2;    -   the second electric machine EM2 can synchronize the shift        element K0    -   a battery-independent serial operation is possible; and    -   the second electric machine EM2 can be used as a generator, the        first electric machine EM1 can be used as a motor.

Finally, FIGS. 9 through 14 show modifications of the exampletransmissions G from FIGS. 2, 3, 5 as well as FIG. 6. Thesemodifications relate to alternative possibilities for integrating theelectric machine EM1, although the example modifications can also beutilized, in a similar way, for the further electric machine EM2 in thetransmissions G according to FIG. 6.

In FIG. 9, for example, the electric machine EM1 is not locatedcoaxially to the particular gear set RS (not represented in greaterdetail here) of the transmission G, but rather is arranged axiallyoffset with respect thereto. A connection takes place via a spur gearstage SRS, which is composed of a first spur gear SR1 and a second spurgear SR2. The first spur gear SR1 is connected at the second input shaftGW2 in a rotationally fixed manner on the side of the particular gearset RS. The spur gear SR1 then meshes with the spur gear SR2, which islocated on an input shaft EW of the electric machine EM1 in arotationally fixed manner. Within the electric machine EM1, the inputshaft EW establishes the connection at the rotor (not representedfurther in this case) of the electric machine EM1.

In the case of the example modification according to FIG. 10 as well,the electric machine EM1 is located axially offset with respect to theparticular gear set RS of the particular transmission G. In contrast tothe preceding example variant according to FIG. 10, a connection is notestablished in this case via a spur gear stage SRS, however, but rathervia a flexible traction drive mechanism ZT. This flexible traction drivemechanism ZT can be configured as a belt drive or also a chain drive.The flexible traction drive mechanism ZT is then connected at the secondinput shaft GW2 on the side of the particular gear set RS. Via theflexible traction drive mechanism ZT, a coupling to an input shaft EW ofthe electric machine EM1 is then established. Within the electricmachine EM1, the input shaft EW establishes a connection at the rotor ofthe electric machine.

In the case of the example modification according to FIG. 11, anintegration of the electric machine EM1, which is located axially offsetwith respect to the particular gear set RS, is implemented via aplanetary gear stage PS and a spur gear stage SRS. The planetary gearstage PS is connected downstream from the gear set RS, wherein, on theoutput end of the planetary gear stage PS, the spur gear stage SRS isthen provided, via which the connection to the electric machine EM1 isestablished. The planetary gear stage PS includes a ring gear HO, aplanet carrier PT, and a sun gear SO, wherein the planet carrier PTguides, in a rotatably mounted manner, at least one planet gear PR,which is meshed with the sun gear SO as well as with the ring gear HO.

In the present case, the planet carrier PT is connected at the secondinput shaft GW2 in a rotationally fixed manner on the side of the gearset RS from FIGS. 2, 3, 5 as well as FIG. 6. By comparison, the ringgear HO is permanently fixed at the rotationally fixed component GG,while the sun gear SO is rotationally fixed to a first spur gear SR1 ofthe spur gear stage SRS. The first spur gear SR1 then intermeshes with asecond spur gear SR2 of the spur gear stage SRS, which is provided, in arotationally fixed manner, on an input shaft EW of the electric machineEM1. In this case, the electric machine EM1 is therefore connected bythe gear set RS via two gear stages.

In the case of the example modification from FIG. 12 as well, anintegration of the electric machine EM1 is implemented by the gear setRS via a planetary gear stage PS and a spur gear stage SRS. Themodification largely corresponds to the example variant according toFIG. 12, with the difference that, with respect to the planetary gearstage PS, the sun gear SO is now fixed at the rotationally fixedcomponent GG, while the ring gear HO is rotationally fixed to the firstspur gear SR1 of the spur gear stage SRS. Specifically, the ring gear HOand the first spur gear SR1 are preferably designed as one piece, inthat the ring gear HO is equipped, at an outer circumference, with atooth system. For the rest, the example modification according to FIG.12 corresponds to the example variant according to FIG. 11, andtherefore reference is made to the description thereof.

Moreover, FIG. 13 shows one further example modification of thetransmissions G from FIGS. 2, 3, 5 as well as FIG. 6, wherein, in thiscase as well, an integration of the electric machine EM1 is implementedvia a spur gear stage SRS and a planetary gear stage PS. In contrast tothe preceding example variant according to FIG. 12, the gear set RS isinitially followed here by the spur gear stage SRS, while the planetarygear stage PS is provided in the power flow between the spur gear stageSRS and the electric machine EM1. The planetary gear stage PS alsoincludes, once again, the elements ring gear HO, planet carrier PT, andsun gear SO, wherein the planet carrier PT guides, in a rotatablymounted manner, multiple planet gears PR1 and PR2, each of which ismeshed with the sun gear SO as well as with the ring gear HO.

As is apparent in FIG. 13, a first spur gear SR1 of the spur gear stageSRS is connected in a rotationally fixed manner on the side of the gearstage RS of the transmissions G from FIGS. 2, 3, 5 as well as 6, whereinthis connection is completed at the second input shaft GW2. The firstspur gear SR1 then intermeshes with a second spur gear SR2 of the spurgear stage SRS, which is rotationally fixed to the planet carrier PT ofthe planetary gear stage PS. The ring gear HO is permanently fixed atthe rotationally fixed component GG, while the sun gear SO is provided,in a rotationally fixed manner, on an input shaft EW of the electricmachine EM1.

Finally, FIG. 14 shows one further example modification of thetransmissions G from FIGS. 2, 3, 5 as well as FIG. 6, wherein thisexample modification essentially corresponds to the preceding examplevariant according to FIG. 10. The only difference is that the sun gearSO of the planetary gear stage PS is now permanently fixed at therotationally fixed component GG, while the ring gear HO of the planetarygear stage PS is rotationally fixed to the input shaft EW of theelectric machine EM1. For the rest, the example modification accordingto FIG. 14 corresponds to the example variant according to FIG. 13, andtherefore reference is made to the description thereof.

Using example embodiments of the invention, a transmission having acompact design and good efficiency can be implemented.

Modifications and variations can be made to the embodiments illustratedor described herein without departing from the scope and spirit of theinvention as set forth in the appended claims. In the claims, referencecharacters corresponding to elements recited in the detailed descriptionand the drawings may be recited. Such reference characters are enclosedwithin parentheses and are provided as an aid for reference to exampleembodiments described in the detailed description and the drawings. Suchreference characters are provided for convenience only and have noeffect on the scope of the claims. In particular, such referencecharacters are not intended to limit the claims to the particularexample embodiments described in the detailed description and thedrawings.

REFERENCE CHARACTERS

-   G transmission-   RS gear set-   GG rotationally fixed component-   P1 first planetary gear set-   E11 first element of the first planetary gear set-   E21 second element of the first planetary gear set-   E31 third element of the first planetary gear set-   P2 second planetary gear set-   E12 first element of the second planetary gear set-   E22 second element of the second planetary gear set-   E32 third element of the second planetary gear set-   A first shift element-   B second shift element-   C third shift element-   D fourth shift element-   E fifth shift element-   F sixth shift element-   K seventh shift element-   K0 eighth shift element-   SP1 shift element pair-   SP2 shift element pair-   SP3 shift element pair-   1 first gear-   2.1 second gear-   2.2 second gear-   2.3 second gear-   2.4 second gear-   2.5 second gear-   3 third gear-   E0 first gear-   E1 second gear-   E3 third gear-   E2 fourth gear-   V1 first gear-   V2.1 second gear-   V2.2 second gear-   V2.3 second gear-   V3 third gear-   GW1 first input shaft-   GW1-A mounting interface-   GW2 second input shaft-   GWA output shaft-   GWA-A mounting interface-   AN connection shaft-   EM1 electric machine-   S1 stator-   R1 rotor-   EM2 electric machine-   S2 stator-   R2 rotor-   SRS spur gear stage-   SR1 spur gear-   SR2 spur gear-   PS planetary gear stage-   HO ring gear-   PT planet carrier-   PR planet gear-   PR1 planet gear-   PR2 planet gear-   SO sun gear-   ZT flexible traction drive mechanism-   VKM internal combustion engine-   TS torsional vibration damper-   AG differential gear-   DW driving wheels

1-17. (canceled)
 18. A transmission (G) for a motor vehicle, comprising:an electric machine (EM1); a first input shaft (GW1); a second inputshaft (GW2); an output shaft (GWA); a first planetary gear set (P1) anda second planetary gear set (P2), the first and second planetary gearsets (P1, P2) each comprising a first element (E11, E12), a secondelement (E21, E22), and a third element (E31, E32); and a first shiftelement (A), a second shift element (B), a third shift element (C), afourth shift element (D), a fifth shift element (E), and a sixth shiftelement (F), wherein a rotor of the electric machine is connected to thesecond input shaft (GW2), wherein the output shaft (GWA) is rotationallyfixed to the second element (E22) of the second planetary gear set (P2),is rotationally fixed to the third element (E31) of the first planetarygear set (P1), and is rotationally fixable to the first input shaft(GW1) with the first shift element (A), wherein the second element (E21)of the first planetary gear set (P1) is rotationally fixed to the thirdelement (E32) of the second planetary gear set (P2), wherein the firstinput shaft (GW1) is rotationally fixable with the second shift element(B) to the second element (E21) of the first planetary gear set (P1) andto the third element (E32) of the second planetary gear set (P2),wherein the first element (E12) of the second planetary gear set (P2) isfixable at a rotationally fixed component (GG) with the third shiftelement (C), wherein the first element (E11) of the first planetary gearset (P1) is fixable at the rotationally fixed component (GG) with thefourth shift element (D), wherein the second input shaft (GW2) isrotationally fixable to the second element (E21) of the first planetarygear set (P1) with the fifth shift element (E) and is rotationallyfixable to the first element (E11) of the first planetary gear set (P1)with the sixth shift element (F).
 19. The transmission (G) of claim 18,wherein selective engagement of the selective engagement of the first,second, third, fourth, fifth, and sixth shift elements (A, B, C, D, E,F) implements: a first gear (1) between the first input shaft (GW1) andthe output shaft (GWA) by engaging the second shift element (B), thethird shift element (C), and the fifth shift element (E); a second gearbetween the first input shaft (GW1) and the output shaft (GWA) in afirst variant (2.1) by engaging the first shift element (A), the thirdshift element (C), and the fifth shift element (E), in a second variant(2.2) by engaging the first shift element (A), the fourth shift element(D), and the fifth shift element (E), in a third variant (2.3) byengaging the first shift element (A), the second shift element (B), andthe fifth shift element (E); and a third gear between the first inputshaft (GW1) and the output shaft (GWA) by engaging the second shiftelement (B), the fourth shift element (D), and the fifth shift element(E).
 20. The transmission (G) of claim 18, wherein selective engagementof the first, second, third, fourth, fifth, and sixth shift elements (A,B, C, D, E, F) implements: a first gear (1) between the first inputshaft (GW1) and the output shaft (GWA) by engaging the second shiftelement (B), the third shift element (C), and the sixth shift element(F); a second gear between the first input shaft (GW1) and the outputshaft (GWA) in a first variant (2.1) by engaging the first shift element(A), the third shift element (C), and the sixth shift element (F), in asecond variant (2.2) by engaging the first shift element (A), the fourthshift element (D), and the sixth shift element (F), in a third variant(2.3) by engaging the first shift element (A), the second shift element(B), and the sixth shift element (F); and and a third gear between thefirst input shaft (GW1) and the output shaft (GWA) by engaging thesecond shift element (B), the fourth shift element (D), and the sixthshift element (F).
 21. The transmission (G) of claim 18, wherein: afirst gear (E0) results between the second input shaft (GW2) and theoutput shaft (GWA) by engaging the third shift element (C) and the sixthshift element (F); a second gear (E1) results between the second inputshaft (GW2) and the output shaft (GWA) by engaging the third shiftelement (C) and the fifth shift element (D); and a third gear (E3)results between the second input shaft (GW2) and the output shaft (GWA)by engaging the fourth shift element (D) and the fifth shift element(E).
 22. The transmission (G) of claim 18, further comprising a seventhshift element (K) arranged and configured for either rotationally fixingtwo elements of the first planetary gear set to each other orrotationally fixing two elements of the second planetary gear set toeach other.
 23. The transmission of claim 22, wherein an additionalelectric gear E2 is implementable between the second input shaft (GW2)and the output shaft (GWA) by engaging the fifth shift element (E) andthe seventh shift element (K).
 24. The transmission (G) of claim 18,further comprising an additional electric machine (EM2), a rotor (R2) ofthe additional electric machine (EM2) connected at the first input shaft(GW1).
 25. The transmission (G) of claim 18, further comprising aneighth shift element (K0), the first input shaft (GW1) rotationallyfixable to a connection shaft (AN) with the eighth shift element (K0).26. The transmission (G) of claim 18, wherein one or more of the first,second, third, fourth, fifth, and sixth shift elements (A, B, C, D, E,F) is a form-locking shift element.
 27. The transmission (G) of claim18, wherein one or both of the first and second planetary gear sets (P1,P2) is a minus planetary gear set, wherein the first element (E11, E12)of each minus planetary gear set is a respective sun gear, the secondelement (E21, E22) of each minus planetary gear set is a respectiveplanet carrier, and the third element (E31, E32) of each minus planetarygear set is a respective ring gear.
 28. The transmission (G) of claim18, wherein: the first shift element (A) and the second shift element(B) are combined to form a shift element pair (SP1); an actuatingelement is associated with the shift element pair (SP1); and the shiftelement pair (SP1) is configured such that either the first shiftelement (A) or the second shift element (B) is engageable by theactuating element from a neutral position of the actuating element. 29.The transmission (G) of claim 18, wherein: the third shift element (C)and the fourth shift element (D) are combined to form a shift elementpair (SP2); an actuating element is associated with the shift elementpair (SP2); and the shift element pair (SP2) is configured such thateither the third shift element (C) or the fourth shift element (D) isengageable by the actuating element from a neutral position of theactuating element.
 30. The transmission (G) of claim 22, wherein: thethird shift element (C) and the seventh shift element (K) are combinedto form a shift element pair (SP2); an actuating element is associatedwith the shift element pair (SP2); and the shift element pair (SP2) isconfigured such that either the third shift element (C) or the seventhshift element (G) is engageable by the actuating element from a neutralposition of the actuating element.
 31. The transmission (G) of claim 18,wherein: the fifth shift element (E) and the sixth shift element (F) arecombined to form a shift element pair (SP3); an actuating element isassociated with the shift element pair (SP3); and the shift element pair(SP3) is configured such that either the fifth shift element (E) or thesixth shift element (F) is engageable by the actuating element from aneutral position of the actuating element.
 32. The transmission (G) ofclaim 18, wherein the rotor (R1) of the electric machine (EM1) isrotationally fixed to the second input shaft (GW2) or is connected tothe second input shaft (GW2) with at least one gear stage.
 33. A motorvehicle drive train for a hybrid or electric vehicle, comprising thetransmission (G) of claim
 18. 34. A method for operating thetransmission (G) of claim 18, wherein the second shift element (B) andthe fifth shift element (E) are engaged in order to implement a chargingoperation or a starting operation.